If you can figure out 3D-Coat well enough, this should be relatively easy to learn. It has nowhere near the features that 3D-Coat has, but if you're looking for something a little more simple to do basic sculpting, it will fit your needs.

It can export to .obj, which can then be imported to 3D-Coat, but I'm not sure how well that works.

I haven't used 3D-Coat much, so I hopped into both to do something quick, export to .obj and import into 3D-Coat. Just going from "Choose Tool to Start" and trying to open it for Voxel Sculpting didn't work too well, but Importing To AUTOPO worked nicely.

Someone with more experience in 3D-Coat can probably figure out something better, I don't know if I did anything wrong, but it at least can be brought in how I did it well enough.

That is Irrelevant: Rhino? Rhino is a nurbs modeler with a reputation of being able to work on files that crash other modelers. The closest tool available in Rhino is the typical lathe tool... if you've used one, then imagine lathes modifying other lathes... using Rhino would probably make learning Shade3d easier(it's greenlit), but not Curvy3d. You can try the Curvy3d demo.